[PATCHv2 1/3] tracing - buf iterator definition, parsing function

[jolsa]

Defined 'trace_biter' structure to carry the properties of the input,
through the multiple writes.

The 'trace_get_user' reads the user incput string separated by space
(matched by isspace(ch). For each string found the 'struct trace_biter' 
iterator is updated, and the function returns.

wbr,
jirka

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>

---
 kernel/trace/trace.c |   83 ++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace.h |   48 +++++++++++++++++++++++++++++
 2 files changed, 131 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index af15008..8cf8f99 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -335,6 +335,89 @@ static struct {
 
 int trace_clock_id;
 
+/*
+ * trace_get_user - reads the user incput string separated by  space
+ * (matched by isspace(ch))
+ *
+ * For each string found the 'struct trace_biter' iterator is updated,
+ * and the function returns.
+ *
+ * Returns number of bytes read.
+ *
+ * see kernel/trace/trace.h for 'struct trace_biter' details.
+ */
+int trace_get_user(struct trace_biter *biter, const char __user *ubuf,
+	size_t cnt, loff_t *ppos)
+{
+	char ch;
+	size_t read = 0;
+	ssize_t ret;
+
+	if (!*ppos)
+		TRACE_BITER_CLEAR(biter);
+
+	ret = get_user(ch, ubuf++);
+	if (ret)
+		goto out;
+
+	read++;
+	cnt--;
+
+	/*
+	 * If the parser haven't finished with the last write,
+	 * continue reading the user input without skipping spaces.
+	 */
+	if (!biter->cont) {
+		/* skip white space */
+		while (cnt && isspace(ch)) {
+			ret = get_user(ch, ubuf++);
+			if (ret)
+				goto out;
+			read++;
+			cnt--;
+		}
+
+		/* only spaces were written */
+		if (isspace(ch)) {
+			*ppos += read;
+			ret = read;
+			goto out;
+		}
+
+		biter->idx = 0;
+	}
+
+	/* read the non-space input */
+	while (cnt && !isspace(ch)) {
+		if (biter->idx < biter->size)
+			biter->buffer[biter->idx++] = ch;
+		else {
+			ret = -EINVAL;
+			goto out;
+		}
+		ret = get_user(ch, ubuf++);
+		if (ret)
+			goto out;
+		read++;
+		cnt--;
+	}
+
+	/* We either got finished input or we have to wait for another call. */
+	if (isspace(ch)) {
+		biter->buffer[biter->idx] = 0;
+		biter->cont = 0;
+	} else {
+		biter->cont = 1;
+		biter->buffer[biter->idx++] = ch;
+	}
+
+	*ppos += read;
+	ret = read;
+
+out:
+	return ret;
+}
+
 ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
 {
 	int len;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d881015..d4e38e8 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -652,6 +652,54 @@ static inline int ftrace_trace_task(struct task_struct *task)
 #endif
 
 /*
+ * struct trace_biter - servers for reading the user input separated by spaces
+ * @cont: set if the input is not complete - no final space char was found
+ * @buffer: holds the parsed user input
+ * @idx: user input lenght
+ * @size: buffer size
+ */
+struct trace_biter {
+	bool		cont;
+	char		*buffer;
+	unsigned	idx;
+	unsigned	size;
+};
+
+#define TRACE_BITER_LOADED(biter) (biter->idx)
+#define TRACE_BITER_CONT(biter)   (biter->cont)
+#define TRACE_BITER_CLEAR(biter) \
+do { \
+	biter->cont = false; \
+	biter->idx = 0; \
+} while(0)
+
+/*
+ * trace_biter_alloc - allocates the buffer for trace buffer iterator
+ */
+static inline int trace_biter_alloc(struct trace_biter *biter, int size)
+{
+	memset(biter, 0, sizeof(*biter));
+
+	biter->buffer = kmalloc(size, GFP_KERNEL);
+	if (!biter->buffer)
+		return 1;
+
+	biter->size = size;
+	return 0;
+}
+
+/*
+ * trace_biter_free - frees the buffer for trace buffer iterator
+ */
+static inline void trace_biter_free(struct trace_biter *biter)
+{
+	kfree(biter->buffer);
+}
+
+extern int trace_get_user(struct trace_biter *biter, const char __user *ubuf,
+	size_t cnt, loff_t *ppos);
+
+/*
  * trace_iterator_flags is an enumeration that defines bit
  * positions into trace_flags that controls the output.
  *
-- 
1.6.2.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/